1. Ecological theory predicts that the soil seed bank stabilizes the composition of annual plant communities in the face of environmental variability. However, long‐term data on the community dynamics in the seed bank and the standing vegetation are needed to test this prediction.
2. We tested the hypothesis that the composition of the seed bank undergoes lower temporal variability than the standing vegetation in a 9‐year study in Mediterranean, semi‐arid and arid ecosystems. The composition of the seed bank was estimated by collecting soil cores from the studied sites on an annual basis. Seedling emergence under optimal watering conditions was measured in each soil core for three consecutive years, to account for seed dormancy.
3. In all sites, the composition of the seed bank differed from the vegetation throughout the years. Small‐seeded and dormant‐seeded species had a higher frequency in the seed bank than in the standing vegetation. In contrast, functional group membership (grasses vs. forbs) did not explain differences in species frequency between the seed bank and the vegetation after controlling for differences between grasses and forbs in seed mass and seed dormancy.
4. Contrary to predictions, the magnitude of year‐to‐year variability (the mean compositional dissimilarity between consecutive years) was not lower in the seed bank than in the vegetation in all sites. However, long‐term compositional trends in the seed bank were weaker than in the vegetation in the Mediterranean and semi‐arid sites. In the arid site where year‐to‐year variability was highest, no long‐term trends were observed.
5. Synthesis. The effect of the seed bank on the temporal variability of the vegetation in annual communities depends on site conditions and time‐scale. While the year‐to‐year variability of the seed bank is similar to the vegetation, the soil seed bank can buffer long‐term trends.

中文翻译：

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土壤种子库可以缓冲一年生植物群落中的长期组成变化

1. 生态学理论预测，面对环境变化，土壤种子库可以稳定一年生植物群落的组成。但是，需要有关种子库和立地植被群落动态的长期数据来检验这一预测。
2. 在地中海，半干旱和干旱生态系统的一项为期9年的研究中，我们检验了以下假设，即种子库的成分的时空变异性低于站立植被的时空变异性。种子库的组成是通过每年从研究地点收集土壤核心来估算的。连续三年在每个土壤核心中测量最佳灌溉条件下的幼苗出苗，以解决种子休眠的问题。
3. 在所有地点，这些年来种子库的组成与植被不同。种子库中的小种子和休眠种子物种比站立的植被具有更高的频率。相反，在控制了草和草之间的种子质量和种子休眠的差异之后，功能组成员身份（草与草）不能解释种子库和植被之间物种频率的差异。
4. 与预测相反，种子库中年际变化的幅度（连续几年之间的平均成分差异）并不低于所有地点的植被。但是，种子库的长期组成趋势要弱于地中海和半干旱地区的植被。在年际差异最大的干旱地区，未观察到长期趋势。
5. 综合。种子库对年度群落中植被时间变化的影响取决于场地条件和时间尺度。尽管种子库的逐年变化与植被相似，但土壤种子库可以缓冲长期趋势。